Three-dimensional image display apparatus

ABSTRACT

A three-dimensional image display apparatus includes an image display configured to output image light which arrays a plurality of pixels and has polarization, a lens array arranged in front of the image display, configured to function as lens at light which has a 1st polarization direction, and not to function as lens at light which has a 2nd polarization direction differed from the 1st polarization direction, and a birefringent phase modulator placed between the image display and the lens array and configured to rotate a polarization plane of the image light.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. JP2003-029281 field on Feb. 6,2003, of which the entire contents are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an autostereoscopic three-dimensionalimage display, and more particularly, relates to an autostereoscopicthree-dimensional image display capable of displaying a two-dimensionalimage and three-dimensional image.

DESCRIPTION OF THE BACKGROUND

A technique of synthetically displaying images from a plurality ofdirections using an image display surface, and making the image appearthree-dimensional according to a viewpoint of an observer is proposed asa three-dimensional display system using a two-dimensional planedisplay.

As the three-dimensional display system, existing techniques may use abinocular stereoscopic system which displays two images observed inviewpoints of right and left eyes, and a multi-view system whichdisplays many images observed in a plurality of viewpoints. Moreover,there exists an Integral Photography method (IP method) whichsynthetically displays images in an image display surface to manydirections, without respect to a particular viewpoint.

As a method to select the image, a method using a pinhole array or aslit array having masked parts and aperture parts, and a methodarranging a lens array or a lenticular array on the image displaysurface, and making an image-formation position of a lens a pixelposition, are known. It is more desirable to use the lens array sincedisplay brightness is reduced using techniques relying on masked parts.

In order to display the two-dimensional image and the three-dimensionalimage alternatively on a same display, various proposals of techniquesfor have been made. One method using a lens array utilizes a selectiondisplay technique switching an existence of a lens effect by making thelens into a refractive index variable layer, has been previouslydisclosed, for example, in Japan Patent Application KOKAI No.2000-102038. Here, it is said that a liquid crystal lens which iscontrolled by an alignment of liquid crystal by voltage, as a refractiveindex control means. By switching the existence of a lens effect, incase the two-dimensional image is displayed, it becomes possible todisplay an image in the original resolution of the two-dimensionaldisplay.

Moreover, as a realization method of a liquid crystal lens, a method ofenclosing liquid crystal material between a convex or a concave lens anda substrate has been disclosed in S. Sato, J. J. App. Phys. Vol. 18, NO.9, (1979) p. 1679–1684. A method of using a Fresnel-lens has beendisclosed in S. Sato et al., J. J. App. Phys. Vol. 24, NO. 8, (1985) p.L626–L628. A method of using a diffractive lens which gives modulationof refractive index to an inside of a plane of incidence has beendisclosed in S. T. Kowel et al., App. Optics Vol. 23, NO. 2, (1984) p.278–289. A method of using a refractive index profile lens which givesmodulation of refractive index to an inside of a plane of incidence anda propagation direction of light has been disclosed in T. Nose et al.,Liquid Crystals Vol. 5, NO. 5, (1989) p. 1425–1433.

SUMMARY OF THE INVENTION

According to embodiments of the present invention, a three-dimensionalimage display apparatus includes an image display having a plurality ofpixels arranged in an array, wherein the image display is configured toprovide image light having a polarization, a lens array arranged infront of the image display, configured to function as lens for lighthaving a first polarization direction, and not function as a lens forlight having a polarization direction perpendicular to the firstpolarization direction, and a birefringent phase modulator placedbetween the image display and the lens array, wherein the birefringentphase modulator is configured rotate a polarization plane of the imagelight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structure of an autostereoscopic three-dimensional imagedisplay apparatus according to the first embodiment of the presentinvention;

FIG. 2 is a sectional view explaining a structure of a liquid crystallens and lens effect;

FIG. 3 shows the image-formation characteristics displayed athree-dimensional image with the liquid crystal lens;

FIG. 4 shows a control block according to the first embodiment;

FIG. 5 shows a structure of an autostereoscopic three-dimensional imagedisplay apparatus according to the second embodiment of the presentinvention;

FIG. 6 is a sectional view showing a structure of the autostereoscopicthree-dimensional image display apparatus according to the secondembodiment;

FIG. 7 shows a control block according to the second embodiment;

FIG. 8 shows a relation between a display mode, and states of appliedvoltage and polarization;

FIG. 9 shows a sequence at changing an image display mode consistentwith the second embodiment of the present invention;

FIG. 10 shows a structure of an autostereoscopic three-dimensional imagedisplay apparatus according to the third embodiment of the presentinvention;

FIG. 11 shows a structure of a liquid crystal cell using passive matrix;

FIG. 12 shows a control block according to the third embodiment;

FIG. 13 is a front view showing a relation of the drive state of theautostereoscopic three-dimensional image display area and a liquidcrystal cell;

FIG. 14 shows a case of window screen according to the third embodiment;

FIG. 15 shows a flow chart of moving a window display position;

FIG. 16 shows a block diagram of an autostereoscopic three-dimensionalimage display apparatus according to the forth embodiment of the presentinvention;

FIG. 17 is a sectional view showing a structure of an autostereoscopicthree-dimensional image display apparatus according to the forthembodiment; and

FIG. 18 shows a control block according to the forth embodiment.

DETAILED DESCRIPTION

An autostereoscopic three-dimensional image display apparatus consistentwith embodiments of the present invention will be described below indetail with references to the accompanying drawings. Wherever possible,the same reference numbers will be used throughout the drawings to referto the same or like parts.

In addition, in the applicable drawings, a z-axis is a direction of anobserver from a display, an x-axis is a horizontal direction (right andleft), and a y-axis is a vertical direction (upper and lower), within ascreen of a display.

(First Embodiment)

FIG. 1 shows an autostereoscopic three-dimensional image displayapparatus according to the first embodiment in present invention.

The autostereoscopic three-dimensional image display may use a LiquidCrystal Display (LCD) 1 as a image display, a birefringent lens array 6which may have a lenticular effect using a lens pitch almost equal to anintegral multiple of a pixel spacings found in LCD 1, and may also use ahalf-wave film 5 having a passively modulated retardation. As usedherein, light projecting from the image display to the lens array iscalled an image light. The image display may use a spontaneous lightemission or it may use a backlight; however, regardless of the method ofgeneration, light emitted from the image display is referred to as imagelight.

Further referring to FIG. 1, the LCD 1 may have a liquid crystal cell 3,and polarization plates 2, and 4, wherein the liquid crystal cell 3 maybe sandwiched between the polarization plates 2 and 4. In the liquidcrystal 3, a liquid crystal may be sandwiched between transparentsubstrates. The LCD 1 may display a three-dimensional or atwo-dimensional image.

A backlight (not shown in FIG. 1), may be arranged in back of apolarization plate 2, and a display image may composed by the imagelight which may be a linear polarized light 9 coincident with atransmissive axis 8 of the polarization plate 4 at light emission side.

The LCD 1 may be a Twisted Nematic (TN) mode, and a direction of thepolarization transmissive axis 8 may be θ=45 degrees, in order to keepviewing angle symmetric in a horizontal direction (i.e., the xz-plane).

The half-wave film 5 may be an optical film which comprisesheat-resistant transparent resin (e.g., norbornene and/or polycarbonateoptical resin) which may have birefringence, may be located at θ=22.5degrees as a phase axis direction 10 which may be prescribed by a fastaxis or a slow axis. The half-wave film 5 may convert an incident linearpolarized light 9 to a output polarized light 11 of θ=0 degrees as apolarized direction by a 45 degrees rotation operation.

Further referring to FIG. 1, the birefringent lens array 6 may be aliquid crystal lens array using the liquid crystal cell aligned with theliquid crystal material which may have a positive dielectric anisotropyand may be inserted between parallel transparent substrates inhomogeneous alignment. That is, the birefringent lens array 6 maygenerate a spatial distribution with an alignment-state of liquidcrystal by applying voltage to comb-like electrodes arranged in theliquid crystal cell by an applying voltage unit 7, and result in a lenseffect. In an alignment direction of the liquid crystal, a direction ofa molecule long-chain axis (director) may be θ=0 degrees, thelongitudinal direction of the comb-like electrodes may be in thedirection of the y-axis, and may be arranged in the direction of thex-axis in the predetermined pitch. Therefore, an electric fielddistribution becomes symmetrical to a yz-plane between the comb-likeelectrodes, and a molecule axis of the liquid crystal may have a spatialdistribution associated to a xz-plane, maintaining θ at 0 degrees.

Consequently, a lenticular effect may occur to an incident polarizationdirection 12 of the θ=0 degree at the time of applying a voltage. Thatis, a lens effect occurs to the incident polarization direction 12 maybe equivalent to a case of which it arranges a lenticular array whichmay have a ridgeline in a direction of a y-axis, and may have apredetermined pitch in a direction of an x-axis. When the voltage is notapplied, since the spatial distribution of liquid crystal alignment maybe lost, a lens effect does not occur.

On the other hand, to an incident polarization direction 13 of θ=90degree, a lens effect may not be applicable because the refractive indexin the direction may correspond to an ordinary refractive indexindependent of alignment-state of the liquid crystal.

FIG. 2 shows a sectional view for explaining a structure of a liquidcrystal lens and lens effect, and provides details about the structureof the lens array 6 and the condensing effect in the liquid crystal.

A common transparent electrode 16 and a set of comb-like electrodes 17may be respectively arranged in parallel transparent substrates 18. A TNmode liquid crystal 15 may be inserted between the transparentsubstrates 18.

Here, in an applying voltage method, there is a case where alternatingvoltage may be applied by using electrodes 16 and 17 as two terminals,and a case which alternating voltage is applied by using the electrodes16, a group in every even lines and a group in every odd lines of thecomb-like electrode 17 as three terminals.

In any case, the spatial distribution of an electric field may begenerated by applying voltage between both the electrodes 16 and 17, andthe lens effect which may have pitch p and a focal length f, occurs tothe polarized component which may have the polarization direction 12.Therefore, a locus of the linear polarized light which may be thepolarization direction 12 can be bent in the propagation within the lensarray 6.

As stated above concerning the alignment-state of the liquid crystallayer 15, it does not have a lens effect to the polarized component 13which may be perpendicular to the polarized component 12 regardless ofthe state of applied voltage because the direction of a moleculelong-chain axis may change only in the xz-plane. Therefore, thepolarized component 13 may propagate in a straight manner within thelens array 6.

In addition, although the dielectric layer, alignment films, etc. forproperly controlling an electric field distribution may be arrangedbetween an electrode and a liquid crystal interface in fact, theillustration abbreviates in FIG. 2.

Therefore, as shown in FIG. 3, the autostereoscopic three-dimensionalimage display of lenticular type works to the linear polarized lightwhich has a polarized component in the direction of an x-axis fromarranging such a lens array 6 so that the pixel 19 of the LCD 1 may belocated in a focal length f.

As explained above, in FIG. 1, the linear polarized light 11 which isimage light can be made in correspondence with the polarizationdirection 12 which may be an effective component of a lens effect whichis generated in the lens array 6 by polarization rotation effect of thehalf-wave film 5.

An output linear polarized light 14, which may have a polarizationdirection of θ=0 degrees at the lens array 6, can be transmitted withconcentration or without concentration by applying or not applying avoltage provided by the applying voltage unit 7. Therefore, the displaychange between the three-dimensional image and a 2-dimensional imagewhich has a maximum resolution of the LCD 1 may be attained by switchingapplying voltage or non-applying voltage of the applying voltage unit 7synchronized with the selection-state of the three-dimensional image andthe 2-dimensional image.

In the case the half-wave film 5 is not used, the polarization directionof an incident image to the lens array 6 may be the linear polarizedlight 9 which may have θ=45 degrees. Therefore, since the polarizedcomponent 13 which may not be an effective component of a lens effect inthe lens 6 can be included in an incident polarized component, the crosstalk which is a multiplexed image may occur in the case of displayingthe three-dimensional image.

On the other hand, the output polarization direction 8 which may haveθ=0 degrees in the LCD 1 may not be desirable with respect to viewingangle characteristics of the LCD 1.

In the case of making the polarization direction having a lens effect anangle at θ=45 degrees with inclining the lens array 6, thethree-dimensional image may not be displayed because parallaxinformation may occur in a slant angle.

Thus, the half-wave film 5 which may be a passive birefringent phasemodulator optimizes display characteristics of the LCD 1, and may have afunction which enables selection of display mode of thethree-dimensional image and the 2-dimensional image using the lens array6 without occurring cross talk.

Although the example of using LCD 1 as the image display which haspolarization as explained above, the image display wherein polarizationis not used, for example, a Cathode Ray Tube (CRT), a Plasma DisplayPanel (PDP), Organic Light Emission Diode (OLED), Organic ElectroLuminescence (EL), Field Emission Display (FED), or other displays knownin the art, can be used by arranging a polarizing plate in front of adisplay surface, in effect providing polarization of the lightcorresponding to the displayed image.

As the lens array, an optical crystal which has birefringence, forexample, calcite, quartz, etc. can be used as a lens by shaping. Thatis, it is not necessary a refractive index is variable in these elementswhich means these may be passive elements. Therefore, the liquid crystallens array which may have birefringence as a passive element can berealized by solidification from a liquid crystal solvent, for example,using a polymerizable liquid crystal or mixing a monomer and a liquidcrystal and polymerizing with ultraviolet rays or heat in the state ofpredetermined alignment.

In order to comprise a lens array with a liquid crystal lens and tocreate a lens effect only in a specific incident polarization direction,it is desirable that a structure encloses liquid crystal materialbetween parallel substrates and the alignment-state of liquid crystal iscontrolled spatially by applied voltage. This may be realizable using adiffractive lens using a predetermined pitch giving a refractive indexdistribution in a incident plane, a refractive index distributed lensgiving a refractive index distribution to a direction of opticalpropagation, or giving a refractive index distribution to both adirection of optical propagation and a plane of incidence.

In order to give a lenticular effect to a specific polarizationdirection, for example, it is may use a homogeneous alignment cell usinga nematic liquid crystal which may have a positive dielectricanisotropy, and arranged perpendicularly a comb-like electrode to aalignment direction of liquid crystal in a predetermined pitch. It ispossible to make a lenticular effect at the time of voltage applying ina specific polarization incident axis, and no lens effect to the otherpolarization incident axis.

Here, the lenticular effect points having a collective effect equivalentto a case where arranged in correspondence with a direction of aridgeline of the lenticular (lens curvature is a direction of infinite)in the direction of a comb-like electrode. Further, with such astructure of a liquid crystal lens, a focus can be made variable bycontrolling applied voltage. By not applying voltage, a lens effect maybe lost, and switching control of the lens effect may be attained bycorrespondingly switching the applied voltage.

FIG. 4 is a view showing a control block diagram to control selectionbetween of a two-dimensional image display and an autostereoscopicthree-dimensional image display according to the first embodiment.

A change selection of the two-dimensional image display and thethree-dimensional display by an observer may transmitted to anautostereoscopic three-dimensional image display-controller 61 throughthe two-dimensional image/autostereoscopic three-dimensional imagedisplay change selection input unit 62 which is switches, such as akeyboard and a mouse.

The autostereoscopic three-dimensional image display-controller 61comprises a graphic controller 63 provided with a display controller 65for controlling an image display of the LCD 1 and an image data 64 fordisplaying an image on the LCD 1, CPU 66, and a birefringent lens arraycontroller 67 for controlling the applying voltage unit 7 of thebirefringent lens array 6.

When an image display-mode selection signal from the observer isreceived, and the selected image display-mode is a three-dimensionalimage, the CPU 66 stores three-dimensional image data in the image data64 and transmits the control signal of applied voltage ON to thebirefringent lens array controller 67.

The birefringent lens array controller 67 may perform setup or controlsfor the parameters of an applied-voltage value, an applied-voltage wave,and frequency to the applying voltage unit 7. On the other hand,three-dimensional image data is displayed on LCD 1 by a graphiccontroller 63, and the three-dimensional image can be observed becausean observer observes three-dimensional image data through thebirefringent lens array 6 which voltage is applied by applying voltageunit 7, and has lens effect.

Similarly, when the two-dimensional image is selected, the CPU 66displays two-dimensional image data on the LCD 1 via the graphiccontroller 63 course, and an observer can observe the equivalenttwo-dimensional image data as the usual LCD through the birefringentlens array 6 without the lens effect by transmitting the control signalof applied voltage OFF to the birefringent lens array controller 67.

In case of a passive element which a rotation angle of the polarizationdirection is fixed, a birefringent phase modulator can use abirefringent phase difference film using a transparent expanded film,and a birefringent optical crystals, such as calcite, quartz, etc.

The birefringent phase modulator is a so-called the half-wave film (orhalf-wave plate) with which retardation has one half to incident-wavelength in order to rotate a plane of polarization. In case of using asingle half-wave film, a phase axis may arrange a rotating angle of theplane of polarization at the angle equally divided to one half, but inorder to mitigate wavelength dispersion and enlarge bandwidth,polarization rotating operations may be performed by using a half-wavefilm or a plurality of phase difference films near a half-wave. Forexample, a method of arranging two half-wave films in directions of 67.5degrees and 22.5 degrees from an optical incident side, in case of thepolarization rotating operation from 0 degree to 90 degrees is known,and it can be applied.

In order to make phase axis rotating of the birefringent phase modulatorvariable, it is suitable to use a liquid crystal cell for thebirefringent phase modulator. In variable phase axis controls, a methodof changing a phase axial angle, and a method of selecting an existenceof a phase axis may be applicable.

In an example of techniques for changing a phase axial angle, liquidcrystal cell modes of Surface Stabilized Ferroelectric Liquid Crystal(SSFLC) using a Ferroelectric Liquid Crystal (FLC) material which mayhave a spontaneous polarization, or Half-V Threshold-LessAnti-Ferroelectric (TLAF) using Anti-Ferroelectric Liquid Crystal (AFLC)material may be applicable. These two modes may be also desirable due totheir speed of response.

Similarly, in the example of the method of selecting the existence of aphase axis, as the liquid crystal cell mode which can realize a fastresponse time such as a PI twist cell (bend alignment cell) usingnematic liquid crystal material can be used.

Further, in case of using phase axis variable control of thebirefringent phase modulator as a matrix type which can be partiallyselected, active matrix switching elements, such as a Thin-FilmTransistor (TFT), may be unnecessary, and it may be desirable to use aliquid crystal cell mode which can be driven by a passive matrix type,i.e., a selection scan of a line-like as an electrode. As such the mode,Super Twisted Nematic (STN) and Bi-stable Twisted Nematic (BTN) modeusing nematic-liquid-crystal material may be applicable.

(Second Embodiment)

FIG. 5 shows a structure of an autostereoscopic three-dimensional imagedisplay apparatus according to the second embodiment in presentinvention.

Similarly to the previous embodiment, the autostereoscopicthree-dimensional image display may have an LCD 1 as a image display, abirefringent lens array 6 which may have a lenticular effect in a lenspitch almost equal to an integral multiple of a pixel spacing of theLCD. A detailed explanation regarding similar elements is provided abovefor the previous embodiment and not duplicated below.

In this embodiment, a ferroelectric-liquid-crystal cell 20 which mayhave a spontaneous polarization may be used as a birefringent phasemodulator. It becomes an active element, which changed a phase axisdirection according to changing displays of a three-dimensional imageand a two-dimensional image.

The ferroelectric-liquid-crystal cell 20 may enclose a ferroelectricliquid crystal among a pair of substrates. Further, on the substrate,electrodes may be arranged, respectively, and voltage can be applied tothe ferroelectric liquid crystal. The ferroelectric-liquid-crystal cell20 may have a spontaneous polarization, and when properly designed, aliquid crystal material and a cell gap works as a half-wave plate.

FIG. 6 is a sectional view showing a structure of the autostereoscopicthree-dimensional image display apparatus according to the secondembodiment. In the ferroelectric-liquid-crystal cell 20, a ferroelectricliquid crystal 39 is arranged between common transparent electrodes 38in transparent substrates 37, an alignment changes by applying voltageto a ferroelectric liquid crystal in an applying voltage unit 21connected to the common transparent electrodes 38, and a phase axisdirection may be changed. Through the ferroelectric-liquid-crystal cell20, a focal length f may be set up on a pixel 19, similarly to thebirefringent lens of the first embodiment. The substrate 3 whichcounters to the ferroelectric-liquid-crystal cell 20 can be common withthe substrate 38 of the ferroelectric-liquid-crystal cell 20.

It is possible to control a phase axis in two states of a 1st phase axisdirection of θ=22.5 degrees (22 in FIG. 5), and a 2nd phase axisdirection θ=67.5 degrees (23 in FIG. 5) by performing a polarity changeof applied voltage using the applying voltage unit 21.

Liquid crystal material may have spontaneous polarization, and since thecell gap may be thin, compared with a relatively slow response time ofthe liquid crystal lens, the ferroelectric-liquid-crystal cell 20 mayquickly respond, for example, in less than 1 ms. Therefore, in case ofchanging a phase axis, it is possible to change by changing the voltagepolarity using the applying voltage unit 21 in a very short period oftime.

If the ferroelectric-liquid-crystal cell 20 is controlled in the 1stphase axis direction 22, when the light of LCD 1 has linear polarization9 of θ=45 degrees, a direction of an output linear polarization 24 fromthe ferroelectric-liquid-crystal cell 20 may become θ=0 degrees. On theother hand, if it controls in the 2nd phase axis direction 23, adirection of an output linear polarization 24 from theferroelectric-liquid-crystal cell 20 may become θ=90 degrees.

Therefore, if the ferroelectric-liquid-crystal cell 20 is controlled bythe 1st phase axis direction 22, the lens array 6 may function as a lensand will serve as an autostereoscopic three-dimensional image displaymode. On the other hand, if controlled by the 2nd phase axis direction23, the lens array 6 may not function as a lens, thus failing to displaya three-dimensional image. In other words, it enters a two-dimensionalimage display mode.

FIG. 7 shows a control block which may perform change control of thetwo-dimensional image/three-dimensional image according to the secondembodiment. The two-dimensional image/three-dimensional image changecontrol unit 69 which controls by applying voltage to the ferroelectricliquid crystal cell 20 and the birefringent lens array 6 comprises aferroelectric liquid crystal cell controller 70 and a birefringent lensarray controller 67, and it is possible to control applied voltage forthe applying voltage unit 7 and 21 independently, respectively.

In present embodiment, when liquid crystal is used for the lens array 6,it is possible to maintain birefringent lens characteristics by applyingvoltage to the lens array 6 regularly, to select the polarity of theapplying voltage unit 21 synchronizing with a selection display of thethree-dimensional image and a two-dimensional image of the imagedisplay, and to make the lens array 6 act as a lens or not to make itact as a lens. Therefore, it is possible to change a display, withoutmaking an observer check by observing undesirable displaycharacteristics which have been generated during a transient responsetime of a liquid crystal lens.

In addition, when the two-dimensional image is displayed continuouslyfor a long period, it may be the lens array 6 in non-applying voltage aswell as the first embodiment from a viewpoint of reducing powerdissipation. Moreover, after a response of the liquid crystal lens iscompleted, even if the ferroelectric-liquid-crystal cell 20 does nothave a memory characteristic, and is non-applied voltage, it is possibleto observe the two-dimensional image.

FIG. 8 shows a relation of states of applying voltage units and outputlinearly polarizations in a two-dimensional image display mode 40 fordisplaying a two-dimensional image continuously for a long period, andthe case of the two-dimensional image display 42 and the case of theautostereoscopic three-dimensional image display 43 in a two-dimensionalimage/three-dimensional image change display mode 41 which changesbetween a two-dimensional image and a three dimensional image by thephase axis direction of the ferroelectric liquid crystal cell 20.

In the two-dimensional image display mode 40, both the applying voltageunit 21 of the ferroelectric liquid crystal cell 20 and the applyingvoltage unit 7 of the birefringent lens array 6 may be in a state ofnon-applied voltage (OFF). Since the birefringent lens array 6 does nothave a lens effect, an alignment-state of theferroelectric-liquid-crystal cell 20 may be in the 1st phase axisdirection or in the 2nd phase axis direction.

On the other hand, in the two-dimensional image/three-dimensional imagechange display mode 41, since voltage is applied by the applying voltageunit 7 of the birefringent lens array 6, the lens effect may occur tothe linear polarization of a direction of θ=0 degrees, and the existenceof the lens effect may be determined by being selected the incidentdirection of the linear polarization to the birefringent lens array 6according to the applied-voltage polarity to theferroelectric-liquid-crystal cell 20.

The change between the two-dimensional image and the three-dimensionalimage in the two-dimensional image/three-dimensional image changedisplay mode 41 can not be observed on an undesirable image during thetransient response because the response of theferroelectric-liquid-crystal cell 20 may be very fast. However, it maybe desirable to change the mode by the predetermined sequence, since achange to the two-dimensional image/three-dimensional image changedisplay mode 41 from the two-dimensional image display mode 40 or achange of an opposite direction accompanies an alignment change of thebirefringent lens array which may have a slow response.

FIG. 9 shows a sequence corresponding to changing image display modes asdescribed above. If a mode selection is performed to the two-dimensionalimage/three-dimensional image change display mode 41 from thetwo-dimensional image display mode 40 by the observer, a positivevoltage polarity +V is applied to the ferroelectric-liquid-crystal cell20 at the time of the two-dimensional image display from the state ofnon-applied voltage (OFF) by the applying voltage unit 21. After asettling period 56 which is when the response of the ferroelectricliquid crystal cell 20 ends completely, a voltage is applied to thebirefringent lens array 6 by the applying voltage unit 7. Although thelens effect may occur gradually to the linear polarization of thedirection of θ=0 degrees in the birefringent lens array 6 during atransient response period 57, since the two-dimensional image displaymay be selected in the ferroelectric-liquid-crystal cell 20, an observedimage display may not change. After the response of the birefringentlens array 6 may be completed, it is possible to select thetwo-dimensional image/three-dimensional image change, and a display modemay be selected by an applied-voltage polarity to the ferroelectricliquid crystal cell 20.

On the other hand, when the mode change from a two-dimensionalimage/three-dimensional image mode 41 to the two-dimensional imagedisplay mode 40 is selected, in reverse order above-mentioned procedure,a two-dimensional image may be displayed in the two-dimensionalimage/three-dimensional image change display mode 41 of theferroelectric-liquid-crystal cell 20, and an applied voltage to thebirefringent lens array 6 may be subsequently made to shift to the stateof non-applying voltage. After a transient response period 60 whereinthe lens effect of the birefringent lens array 6 may disappearscompletely, may ceases to apply voltage to the ferroelectric liquidcrystal cell 20, thus entering the state of non-applying voltage. It ispossible to continue observing two-dimensional image by this sequencefor an observer, without observing the non-desired display. Further, itis also possible to use the lens array 6 which does not depend on liquidcrystal mentioned in a previous embodiment.

(Third Embodiment)

FIG. 10 shows a structure of an autostereoscopic three-dimensional imagedisplay apparatus according to the third embodiment in presentinvention. Moreover, FIG. 13 is a front view showing a relation of thedriving state of the autostereoscopic three-dimensional image displayarea and a liquid crystal cell.

Similar to the previous embodiment, the autostereoscopicthree-dimensional image display may use LCD 1 as an image display, abirefringent lens array 6 which has a lenticular effect in a lens pitchalmost equal to as much as some integral number of times of a pixelpitch of the LCD. A detailed explanation regarding similar elements isprovided above for the previous embodiments and is not duplicated below.

In this embodiment, the birefringent phase modulator may be a liquidcrystal cell 25 in which a matrix drive is possible. The polarizationdirection 4 of the image light in the LCD 1 is explained as θ=0 degreesfor simplicity. Such a polarization plate arrangement can be appliedcharacteristics in Vertically Align (VA), In-Plane-Switching (IPS) mode,etc, without an adverse influence on the visual-angle.

The liquid crystal cell 25 may enclose liquid crystal among a pair ofsubstrates, and an electrode, which applies voltage to liquid crystal,is arranged on the both substrates. This liquid crystal cell 25comprises the electrode of which a matrix drive is possible. Here, thematrix drive may divide a display area of the liquid crystal cell 25into a plurality of areas 30, and applying voltage to the desired domain30, as shown in FIG. 13. As the electrode structure of the matrix drive,a TFT drive for an ordinary liquid crystal display, or a passive matrixdrive which may apply a predetermined voltage pulse, and may have astructure of crossed comb-like electrodes, may be applicable.

As an example of the liquid crystal cell 25 of which a matrix drive ispossible, FIG. 11 is a view showing a structure of a liquid crystal cellusing a STN mode liquid crystal cell of the passive matrix.

In the liquid crystal cell 25, a liquid crystal 81 in STN mode may bearranged between transparent substrates 80 which arranged a comb-liketransparent electrode 82, respectively. The LCD driver is arranged as anapplying voltage unit 27 so that desired voltage can be applied to somedomain 30 by applying the voltage pulse to comb-like transparentelectrodes 82.

FIG. 12 shows a control block according to the third embodiment. Atwo-dimensional image/three-dimensional image change controller 69 has agraphic controller 71 for displaying and controlling a window in adesired position of the liquid crystal cell 25, and controls displayingthe window of the same display position and size in the liquid crystalcell 25 corresponding to a three-dimensional image data partially savedin a image data 64 of a graphic controller 63 by the side of the LCD 1.

In this embodiment, a phase axis may disappear, the polarizationdirection of incident light is transmitted without changing in thedomain 29 which applied voltage to liquid crystal. Moreover, thepolarization direction of incident light is rotated in the domain, whichis not applied voltage. Of course, it is also possible to rotate thepolarization direction of incidence light in the domain, which appliedvoltage, and not to rotate the polarization direction in other domains,based on a kind of using liquid crystal mode.

Referring to FIG. 13, in the domain 29 of the liquid crystal cell 25,since a light is transmitted without changing a polarized component,image light is transmitted by the liquid crystal cell 25 with linearpolarization 9 (θ=0 degrees). The direction of the linear polarization28 which comes out from the liquid crystal cell 25 may be θ=0-degrees,and may enter into the lens array 6. Therefore, in the lens array 6, alens effect may occurs in the domain 29.

On the other hand, since phase axis 26 is θ=45 degrees in a domain ofnon-applied voltage, an output polarization direction of the liquidcrystal cell 25 is rotated at θ=90 degrees, and a lens effect does notoccur in the lens array 6.

As explained above, the liquid crystal cell 25 which fulfills half-waveconditions and in which a matrix drive is possible may be arrangedbetween the image display 1 and the lens array 6, and it is possible todisplay easily the three-dimensional image and the two-dimensional imageon one screen by applying voltage to the domain 29 in part of the liquidcrystal cell 25 by the applying voltage unit 27. For example, in FIG.13, the domain 29 applied voltage is a window area in thetwo-dimensional image displaying area, and it is possible to display thethree-dimensional image in the window. Even if a moving operation of thewindow is commanded by a mouse, it is possible to display thethree-dimensional image on at any positions by moving the domain 29applied voltages synchronizing with the operation.

FIG. 14 shows a case of window screen according to the third embodiment.When the autostereoscopic three-dimensional image display is selected, athree-dimensional image may be displayed on the domain 29. An area 83which is outside of the domain 29 is displayed in high definition bytwo-dimensional image display, and a window control bar for operating awindow and a control button 84 which may select the two-dimensionalimage display and the autostereoscopic three-dimensional image displayin the domain 29 may be arranged in the window control bar domain withthe control buttons which have generally in order to operate to open orclose of the window. Here, it may be desirable that a horizontal displaysize W of the domain 29 is as much as some integral number times of apitch p of the birefringent lens array 6 and a vertical display-size His as much as some integral number of times of a vertical size of theunit domain 30 in the liquid crystal cell 25, and, clipping is carriedout so that the displayed position of the window may be satisfied withthis condition in case of moving, or an expanding operation, etc.

FIG. 15 shows an example of the desirable display sequence of adisplay-position change of a window is operated at the autostereoscopicthree-dimensional image display. When the control bar of the window isselected by the observer (by, for example, “clicking” on a selectedportion of the control strip using a mouse), the three-dimensional imageis not displayed by displaying the predetermined pattern image, etc, asa process of preparation of moving operation, and the display mode ischanged to the two-dimensional image display after that. Furthermore, itmay display a two-dimensional image by checking whether thetwo-dimensional image data corresponding to the three-dimensional imagewhich was displayed exists or not before the display mode change, andperform the process 85 which displays a 2-dimensional picture. Usingthis process, it may not be necessary to update in detail theautostereoscopic three-dimensional image display with changing thedisplay position during the moving operation of the window. Even if theresponse time of the liquid-crystal-display mode is not fast such as STNmode, an undesirable image resulting from the mismatch (response delay)of the displayed position of the image data and the window of the liquidcrystal cell can not be observed. After the moving operation by anobserver is completed, the three-dimensional image is displayed afterchanging to the three-dimensional display mode.

(Fourth Embodiment)

FIG. 16 shows a block diagram of an autostereoscopic three-dimensionalimage display apparatus according to the fourth embodiment in presentinvention. In this embodiment, a half-wave film 5B and liquid crystallens 6B is added to the first embodiment, and given a vertical directionparallax by making a birefringent phase modulator and a lens array totwo-step stricture.

Similarly to the previous embodiment, the autostereoscopicthree-dimensional image display may have LCD 1 as a image display, abirefringent lens array 6 which has a lenticular effect in a lens pitchalmost as much as some integral number of times of a pixel of the LCD. Adetailed explanation regarding similar elements is provided above forthe previous embodiments and is not duplicated here. Moreover, abirefringent phase modulator 5A may be arranged between the LCD 1 andthe lens array 6A.

Newly added lens array 6B may have the same structure as the lens array6A rotated 90 degrees, and has a lenticular effect of the screenvertical direction to polarization direction 12B of θ=90-degree at theapplied voltage. Similarly to the lens array 6A, a focal length of thelens is arranged so that it may be located in the pixel part of LCD 1.

A phase axis direction 10B of added birefringent phase modulator 5B isθ=45-degree direction, rotates the θ=0 degree of the output polarizationdirections of the lens array 6A to 90 degrees, and carries out incidenceto lens array 6B. Thereby, in the light, which carries out incidence tolens array 6B, the lens effect occurs in the lens array 6B.

FIG. 17 shows a sectional view of an autostereoscopic three-dimensionalimage display apparatus according to the forth embodiment. Similar tothe previous embodiment, the focal lengths fA and fB of the birefringentlens array 6A, which generates a vertical direction parallax, and thebirefringent lens array 6B, which generate a horizontal directionparallax, are arranged so that a focus may be located in the pixel 19 ofthe LCD 1. Since the lens effect in both birefringent lens arraysgenerates crosswise in a horizontal direction and a vertical directionof a screen, a focal length may be set up independently with regardlessof a mutual lens state.

Using such a two-step structure, it may be possible to not only displaythe three-dimensional image and the two-dimensional image selectively,but also add freely the horizontal direction parallax and the verticaldirection parallax in the autostereoscopic three-dimensional imagedisplay by controlling applied voltage at each liquid crystal lens 6Aand 6B independently. Moreover, it may be possible to set up a pluralityof parallaxes in the three-dimensional display by dividing the comb-likeelectrode in each liquid crystal lens into some groups and controllingthe groups independently. Since a plurality of conditions can be set upfor numbers of the horizontal direction parallax by a number of verticaldirection parallax, such as 16 by 6 and 32 by 3, it is possible to setup the optimal autostereoscopic three-dimensional image displaycondition adjusting for display contents and observation conditions.

FIG. 18 shows a control block diagram consistent with to the forthembodiment of the invention. The two-dimensional image/three-dimensionalimage change controller 69 which controls the birefringent lens arrays6A and 6B comprises birefringent lens array controllers 67A and 68Bwhich may control each lens array independently. In an image data area64 of a graphic controller 63, a two-dimensional image, or athree-dimensional image data, which has predetermined parallaxesaccording to a display mode, is saved, and is displayed on the LCD 1.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A three-dimensional image display apparatus, comprising: an imagedisplay having a plurality of pixels arranged in an array, wherein theimage display is configured to provide image light having apolarization; a lens array arranged in front of the image display,configured to function as a lens for light having a first polarizationdirection, and not function as a lens for light having a polarizationdirection differing from the first polarization direction; and abirefringent phase modulator placed between the image display and thelens array, wherein the birefringent phase modulator is configured torotate a polarization plane of the image light.
 2. The three-dimensionalimage display apparatus according to claim 1, wherein the birefringentphase modulator has a variable phase axis direction which is controlledby applied voltage.
 3. The three-dimensional image display apparatusaccording to claim 1, wherein the birefringent phase modulator has aphase axis direction being variable on a portion of a screen of theimage display.
 4. The three-dimensional image display apparatusaccording to claim 1, wherein the birefringent phase modulator has phaseaxis directions differed on a screen of the image display.
 5. Thethree-dimensional image display apparatus according to claim 1, whereinthe lens array has a liquid crystal layer and a pair of electrodes whichsandwich the liquid crystal layer, and controls a focal distance byapplying a voltage between the pair of electrodes.
 6. Thethree-dimensional image display apparatus according to claim 1, whereinthe birefringent phase modulator has a liquid crystal layer and a pairof electrodes which sandwich the liquid crystal layer, and configured tocontrol a phase-axis by a polarity of applied voltage to the electrodes.7. The three-dimensional image display apparatus according to claim 6,wherein the birefringent phase modulator is configured to change athree-dimensional image display and a two-dimensional image display bycontrolling the phase-axis according to a selection of athree-dimensional image and a two-dimensional image.
 8. Thethree-dimensional image display apparatus according to claim 1, whereinthe birefringent phase modulator has a liquid crystal layer and a pairof electrodes which sandwich the liquid crystal layer, and configured tocontrol a phase-axis by an applied voltage to the electrodes.
 9. Thethree-dimensional image display apparatus according to claim 8, whereinthe birefringent phase modulator is configured to change athree-dimensional image display and a two-dimensional image display bycontrolling the applied voltage according to a selection of athree-dimensional image and a two-dimensional image.
 10. Thethree-dimensional image display apparatus according to claim 1, whereinthe birefringent phase modulator has a liquid crystal layer which isdriven by a matrix and a pair of electrodes and sandwich the liquidcrystal layer, and configured to control a phase-axis partially by anapplied voltage to the electrodes.
 11. The three-dimensional imagedisplay apparatus according to claim 10, wherein the birefringent phasemodulator is configured to change a three-dimensional image display anda two-dimensional image display partially by controlling the appliedvoltage according to a selection of a three-dimensional image and atwo-dimensional image.
 12. A three-dimensional image display apparatuscomprising: an image display having a plurality of pixels configured inan array, wherein the image display is configured to output an imagelight having polarization; a lens array arranged in front of the imagedisplay, having a liquid crystal layer and a pair of electrodes whichsandwich the liquid crystal layer, and configured to control a lensaction for light having a first polarization direction by applying avoltage; and a birefringent phase modulator arranged between the imagedisplay and the lens array and configured to rotate a polarization planeof the image light.
 13. The three-dimensional image display apparatusaccording to claim 12, wherein one of the electrodes has a comb-likestructure.
 14. The three-dimensional image display apparatus accordingto claim 12, wherein the lens array is configured to change athree-dimensional image display and a two-dimensional image display bycontrolling the applied voltage according to a selection of athree-dimensional image and a two-dimensional image.
 15. Thethree-dimensional image display apparatus according to claim 12, whereinthe birefringent phase modulator has a liquid crystal layer and a pairof electrodes which sandwich the liquid crystal layer, and configured tocontrol a phase-axis by a polarity of applied voltage to the electrodes.16. The three-dimensional image display apparatus according to claim 15,wherein the birefringent phase modulator is configured to change athree-dimensional image display and a two-dimensional image display bycontrolling the phase-axis according to a selection of athree-dimensional image and a two-dimensional image.
 17. Thethree-dimensional image display apparatus according to claim 16, whereinthe lens array is configured to control the applied voltage of the lensarray, when the two-dimensional image is selected by controlling thepolarity of applied voltage of the birefringent phase modulator.
 18. Thethree-dimensional image display apparatus according to claim 12, whereinthe birefringent phase modulator has a liquid crystal layer and a pairof electrodes which sandwich the liquid crystal layer, and configured tocontrol a phase-axis by an applied voltage to the electrodes.
 19. Thethree-dimensional image display apparatus according to claim 18, whereinthe birefringent phase modulator is configured to change athree-dimensional image display and a two-dimensional image display bycontrolling the applied voltage according to a selection of athree-dimensional image and a two-dimensional image.
 20. Thethree-dimensional image display apparatus according to claim 12, whereinthe birefringent phase modulator has a liquid crystal layer which isdriven by a matrix and a pair of electrodes and sandwich the liquidcrystal layer, and configured to control a phase-axis partially by anapplied voltage to the electrodes.
 21. The three-dimensional imagedisplay apparatus according to claim 20, wherein the birefringent phasemodulator is configured to change a three-dimensional image display anda two-dimensional image display partially by controlling the appliedvoltage according to a selection of a three-dimensional image and atwo-dimensional image.
 22. A three-dimensional image display apparatuscomprising: an image display configured to array a plurality of pixelsand output an image light which has polarization; a first lens arrayarranged in front of the image display, has a liquid crystal layer and apair of electrodes which sandwich the liquid crystal layer, andconfigured to control a lens effect to light which has a firstpolarization direction by applied voltage; a second lens array arrangedin front of the first lens array, has a liquid crystal layer and a pairof electrodes which sandwich the liquid crystal layer, and configured tocontrol a lens effect to light which has a second polarization directiondiffered from the first polarization direction by applied voltage; afirst birefringent phase modulator arranged between the image displayand the first lens array and configured to rotate a polarization planeof the image light; and a second birefringent phase modulator arrangedbetween the first lens array and the second lens array and configured torotate a polarization plane of the output light from the first lensarray.